The present invention relates to the use of additives for the protective treatment of wood materials to confer improved oil- and hydro-repellence properties.
Specifically, the invention relates to the addition of additives to the formulations usually utilized for the wood treatment, such as for example impregnating, antivegetative, insecticidal formulations, etc. Said additives are effectively used at very low surface concentrations, avoiding to modify the surface aspect of the treated wood material.
Compounds able to give wood hydro-repellence properties are known in the prior art. U.S. Pat. No. 5,141,983 which describes polyurethane-acrylic copolymers dispersed in water can for example be mentioned. The drawback of these products consists in that they are not able to confer suitable oil-repellence properties.
Other compounds, for example functionalized amino-organo hydrogenated siliconates are described in U.S. Pat. No. 5,178,668. Also for these products, there is the drawback that they are unable to confer suitable oil-repellence properties.
In U.S. Pat. No. 5,855,817 compounds having more than one hydroxyl function in combination with quaternary ammonium salts to confer hydro-repellence to wood, are described. Also in this case the oil-repellence properties are not high.
There are also aqueous formulations based on siliconates, polyurethanes and silicates, described in U.S. Pat. No. 5,356,716. Also in this case no mention is made to possible conferred oil-repellence properties.
Hydrocarbon solvent-based formulations comprising mixtures of fluoropolymers, hydrogenated silanes and silicones are described in U.S. Pat. No. 5,593,483. Also in this case no mention is made to possible conferred oil-repellence properties.
In U.S. Pat. No. 5,691,000 specific perfluoropolyether phosphor monoester compounds able to give hydro- and oil-repellence to wood are described. The solvents used for the dissolution of these compounds are CFC-113 or alcohol/water mixtures. In this patent also other perfluoropolyether compounds having different functionalities are exemplified. The Examples show that these latter derivatives have lower hydro- and oil-repellence properties in comparison with the perfluoropolyether phosphor monoesters. In particular, the hydro-repellence values of phosphor monoesters when applied on wood are unsatisfactory. In fact, the Applicant has noticed that the oil- and hydro-repellence test is not sufficiently discriminating to identify the real protection degree given to wood. For this reason, these products have found a poor commercial application for the protective wood treatment. In this patent no mention is made to the use as additives of said products in the formulations used for wood.
The technical problem that the present invention intends to solve is that to find additives showing the following property combination:
improved hydro-repellence properties;
improved oil-repellence properties;
absence of any change of the wood natural aspect;
substantial maintenance of the properties conferred by impregnating, antivegetative, insecticidal, etc., formulations also after additive addition;
good compatibility of the additive with impregnating, anti-vegetative, insecticidal, etc. formulations so as to have substantially uniform oil- and hydro-repellence properties on the surface of the treated wood;
improvement of the wetting capacities of the above mentioned formulations for wood;
improved friction coefficient, i.e. decrease of the friction coefficient values of the wood surface which implies a wear limitation.
The need was therefore felt to have available additives for formulations used in the wood treatment, able to give the combination of the above mentioned properties.
An object of the invention are therefore mono- and bifunctional perfluoropolyether compounds and their use as additives in formulations for the wood treatment, excluding the formulations based on paraffin waxes dissolved in hydrocarbon solvents, said perfluoropolyether compounds having the following structures:
Rfxe2x80x94CFYxe2x80x94Lxe2x80x94Wxe2x80x83xe2x80x83(C)
Wxe2x80x94Lxe2x80x94YFCxe2x80x94Oxe2x80x94Rfxe2x80x94CFYxe2x80x94Lxe2x80x94Wxe2x80x83xe2x80x83(D)
wherein:
L is an organic group selected from xe2x80x94CH2xe2x80x94(OCH2CH2)nxe2x80x94,
xe2x80x94COxe2x80x94NRxe2x80x2xe2x80x94, with Rxe2x80x2xe2x95x90H or C1-C4 alkyl group;
n=0-8, preferably 1-3;
Yxe2x95x90F, CF3;
W is selected from C1-C50 alkyl groups, preferably C8-C25, optionally containing one or more ether O, C6-C50 aryl groups, C7-C50 alkyl-aryl or aryl-alkyl groups;
Rf has a number average molecular weight in the range 350-8,000, preferably 500-3,000 and it comprises repeating units having at least one of the following structures, statistically placed along the chain:
(CFXO), (CF2CF2O), (CF2CF2CF2O), (CF2CF2CF2CF2O),
(CR4R5CF2CF2O), (CF(CF3)CF2O), (CF2CF(CF3)O),
wherein
Xxe2x95x90F, CF3;
R4 and R5, equal to or different from each other, are selected from H, Cl, or perfluoroalkyl from 1 to 4 carbon atoms.
In particular Rf can have one of the following structures:
1) xe2x80x94(CF2O)axe2x80x2xe2x80x94(CF2CF2O)bxe2x80x2xe2x80x94
with axe2x80x2/bxe2x80x2 in the range 0.5-2, extremes included, axe2x80x2 and bxe2x80x2 being integers such as to give the above mentioned molecular weight;
2) xe2x80x94(C3F6O)rxe2x80x94(C2F4O)bxe2x80x94(CFXO)txe2x80x94
with r/b=0.5-2.0; (r+b)/t is in the range 10-30,
b, r and t being integers such as to give the above mentioned molecular weight, X has the above mentioned meaning;
3) xe2x80x94(C3F6O)rxe2x80x2xe2x80x94(CFXO)txe2x80x2xe2x80x94
txe2x80x2 can be 0;
when txe2x80x2 is different from 0 then rxe2x80x2/txe2x80x2=10-30,
rxe2x80x2 and txe2x80x2 being integers such as to give the above mentioned molecular weight; X has the above indicated meaning;
4) xe2x80x94(OCF2CF(CF3))zxe2x80x94OCF2(Rxe2x80x2f)yxe2x80x94CF2Oxe2x80x94(CF(CF3)CF2O)zxe2x80x94
wherein z is an integer such that the molecular weight is the above mentioned one;
y is an integer between 0 and 1 and Rxe2x80x2f is a fluoroalkylene group having for example 1-4 carbon atoms;
5) xe2x80x94(OCF2CF2CR4R5)qxe2x80x94OCF2(Rxe2x80x2f)yxe2x80x94CF2Oxe2x80x94(CR4R5CF2O)sxe2x80x94wherein:
q and s are integers such that the molecular weight is the above mentioned one;
R4, R5, Rxe2x80x2f, y have the above mentioned meaning;
6) xe2x80x94(C3F6O)rxe2x80x2xe2x80x3(CFXO)txe2x80x2xe2x80x3xe2x80x94OCF2(Rxe2x80x2f)yxe2x80x94CF2O(CF(CF3)CF2O)rxe2x80x2xe2x80x3(CFXO)txe2x80x2xe2x80x3xe2x80x94
wherein rxe2x80x2xe2x80x3/txe2x80x2xe2x80x3=10-30,
rxe2x80x2xe2x80x3 and txe2x80x2xe2x80x3 being integers such as to give the above mentioned molecular weight;
Rxe2x80x2f and y having the above mentioned meaning.
In the above indicated formulas:
xe2x80x94(C3F6O)xe2x80x94 can represent units of formula xe2x80x94(CF(CF3)CF2O)xe2x80x94 and/or xe2x80x94(CF2xe2x80x94CF(CF3)O)xe2x80x94
In the structure (C) wherein Rf is monofunctional, the other end group is of the Txe2x80x94Oxe2x80x94 type, wherein T is a (per) fluoroalkyl group selected from: xe2x80x94CF3, xe2x80x94C2F5, xe2x80x94C3F7, xe2x80x94CF2Cl, xe2x80x94C2F4Cl, xe2x80x94C3F6Cl; optionally one or two F atoms, preferably one, can be replaced by H.
The mentioned fluoropolyethers are obtainable by the well known processes in the prior art, see for example the following patents herein incorporated by reference: U.S. Pat. Nos. 3,665,041, 2,242,218, 3,715,378, and EP 239,123. The functionalized fluoropolyethers are for example obtained according to EP 148482, U.S. Pat. No. 3,810,874.
The compounds of structure (C) are obtained by reacting a monofunctional perfluoropolyether ester derivative with an alkylamine. The alkylamine, generally under waxy form, is melted at a temperature in the range 40xc2x0-60xc2x0 C. The perfluoropolyether ester derivative is dropped in the amine in an equimolar amount under stirring and maintaining the reactor at the desired temperature. At the end of the addition the alcohol which has formed from the condensation reaction is evaporated.
The compounds of structure (D) are obtained by reacting a bifunctional perfluoropolyether ester derivative with an alkylamine. The alkylamine, generally under waxy form, is melted at a temperature in the range 40xc2x0-60xc2x0 C. The bifunctional perfluoropolyether ester derivative is dropped in the amine in molar amount 0.5 with respect to the amine under stirring and maintaining the reactor at the desired temperature. At the end of the addition the alcohol which has formed from the condensation reaction is evaporated.
The preferred compounds of the invention have structure (D) wherein L is xe2x80x94COxe2x80x94NRxe2x80x2xe2x80x94, with Rxe2x80x2xe2x95x90H; W is a C8-C25 alkyl group; Rf has structure 1).
Mixtures of the above mentioned compounds (C) and (D) can also be used.
The Applicant has surprisingly found that by using the above defined perfluoropolyether derivatives as additives of formulations for the wood treatment, the combination of the above mentioned properties is obtained. This result is unexpected since the same compounds of structure (C) and (D) not used as additives in formulations for wood, but used alone as treating agents are not able to confer high oil- and hydro-repellence properties, the concentrations being the same. The Applicant has found that in order to obtain comparable hydro- and oil repellence values on wood, when the components of the invention are used alone dispersed in solvents, it is necessary to carry out repeated treatments (at least 3). From the industrial point of view this represents a remarkable application drawback besides higher costs.
The formulations for wood to which the additives of the invention are added are those known for the wood treatment: impregnating, antivegetative, insecticidal, anti-mould formulations, paints, etc. can be mentioned. Preferably said formulations for wood are based on solvents, such as for example ketones, alcohols, glycols, hydrocarbons.
The impregnating formulations prevailingly comprise as main components natural oils, acrylic and polyurethane polymers. The anti-vegetative formulations prevailingly comprise as main components limonene, alkyd resins and fluorinated acrylic polymers. The insecticidal formulations prevailingly comprise as main components dichlofluoranid, permethrin, linseed oil and dibutylphthalate.
The additives of the invention are added to the formulations in concentrations in the range 0.01-10% by weight, preferably 0.1-5% by weight with respect to the formulation weight. The application of the formulation can be carried out by brushing, spraying, etc. Optionally, if required by the industrial application process, after the treatment a thermal treatment can be carried out for a quicker removal of the solvent.
The present invention will be better illustrated by the following Examples, which have a merely indicative but not limitative purpose of the scope of the invention itself.